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Inventories (Details Textual) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2017
Inventories (Textual)          
Inventory write-down $ 494,896 $ 557,668 $ 1,199 $ 1,199